Werndls are really NEAT! Think of a Snider, but the block ROLLS instead of hinging up and out.
There were at least 3 basic models. Some were converted muzzle-loaders, some were made new as breechloaders, but they are all NEAT. They used to sell in Canada for $11.97, plus shipping, from Albion Arms in Peterborough. I had the requisite $11.97 but got a Vetterli-Vitali instead. Now I ask Santa for a Werndl every year and the old fart ignores me!
You could load smokeless in this if you were VERY careful. SR-4759 can substitute for Black at a 38-percent-of-Black charge by WEIGHT ratio and give you the original performance with low pressures.
There were also 2 different cartridges for the Werndl, and some of the older rifles were modded for the later 1877 cartridge. Barnes (COTW-6) shows loads for the 1877 cartridge but not for the early one.
TEXT BOOK OF SMALL ARMS - 1909 gives this round (the later one, I do believe) as follows:
Cartridge overall length: 3.07 inches
Cartridge weight: 656 grains
Bullet material: lead
Bullet length: 1.063 inches
Bullet diameter: .433 inch
Bullet weight: 370 grains
Powder charge: 77.16 grains
Value of W/d-squared: .282
Muzzle velocity: 1,440 ft/sec
Hope this helps.